This invention relates generally to teletext (TTX) systems and particularly to teletext systems having multiple page memory storage. Teletext systems, wherein primarily textual information is transmitted during the vertical blanking intervals of a television signal, have been known for some time. Such systems have been slow to gain popularity in the United States, although they have been in use in Europe for a number of years. To obtain the benefits of teletext transmissions, a teletext processor or decoder is required. Generally, processor circuitry is incorporated into a television receiver to enable acquisition of the transmitted data and the storing of that data in a teletext page memory. The teletext signal format involves a series of magazines each having up to 100 pages that are transmitted one after the other in a cyclical manner. TTX data is acquired by means of user entered magazine and page number requests. When a circulating page of TTX data has been acquired, the information is displayed on the cathode ray tube (CRT) in the viewer's television receiver. Some teletext processors have relatively large memories and are capable of acquiring a plurality of pages of TTX data. In U.S. Pat. No. 4,388,645, multiple page storage of TTX data is provided in a cable system. In that arrangement, the cable head-end is provided with means for acquiring a multiplicity of teletext pages and for arranging for their appropriate transmission at predetermined times.
In the publication, Digit 2000 VLSI Digital TV System, Edition 1984/5, by Intermetall Semiconductors of ITT, which publication is hereby incorporated by reference, a teletext processor unit (TPU) is described in which up to eight pages may be acquired in response to appropriate user input commands. Minimum acquisition delay would be experienced when reading through the pages of TTX data that are in the memory.
The system described in the Digit 2000 publication thus provides for easy and fast "paging" among a group of user preselected teletext pages. The system of the U.S. Pat. No. 4,388,645 patent provides for retransmission of previously acquired pages of TTX data based upon a time code inserted by the cable operator, when the data is acquired. The present invention is directed to a system in which responsive to a user request for a desired page of TTX data, a number of predetermined adjacent pages of TTX data are automatically acquired and placed in memory and are readily available for viewing in response to simple page up and page down commands.